Researchers looked at four different studies involving flu vaccines and heart health. The studies included more than 3,000 patients, half of whom had confirmed heart disease.
Half of the participants received the flu vaccine and half a placebo.
After one year, those who received the flu vaccine had a 50% reduced risk of suffering major cardiac events like heart attack and stroke, and a 40% reduced risk of heart related death.
St. Vincent cardiologist Doug Borg says the flu causes inflammation that can aggravate unstable plaques in the heart.
"The idea is the inflammation triggers something in the plaque to rupture. Once it does that, it breaks through the lining of the artery and causes a blood clot. The body treats it like a cut, it tries to heal that area much like placing a scab on your skin, but unfortunately that blocks the blood flow to that artery, thus precipitating a heart attack."
In another study, cardiologists looked at the role of flu vaccines among patients with implantable cardiac defibrillators.
Researchers focused on 230 patients between the ages of 70 and 74 with ICD's.
On average, those who opted out of the vaccine had more shocks from their defibrillators during flu season.
"People don't think of the flu as a major illness, but over 90,000 people have heart attacks simply related to the flu every year compared to people that don't have the flu. It can be a significant stress on the body, especially for older people or people with other comorbid diseases.
Researchers say larger-scale studies are needed to support their findings. The American Heart Association does recommend everyone ages 6 months and older receive the flu vaccine.